Reduction of explosive joint edge degradation



Oct. 19, 1965 J. v. BURMAN ETAL 3,212,183

REDUCTION OF EXPLOSIVE JOINT EDGE DEGRADATION Filed Dec. 28, 1962 F'IGJ Ilflllli LFFZFIII INVENTORS JOHN V- BURMAN MANLY J. MILLER FREDERICK C. POLHEMUS,JR BY W1;

AGENT United States Patent 3,212,183 REDUCTION OF EXPLOSIVE JOINT EDGE DEGRADATIDN John V. Barman, West Palm Beach, Manly J. Miller,

Jupiter, and Frederick C. Polhemus, Jin, Lake Park,

Fla., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Dec. 28, 1962, Ser. No. 248,000 Claims. (Cl. 29470.1)

This invention relates to the formation of a joint between two materials capable of being joined by an explosive charge in which the end of the movable plate is susceptible to degradation or breaking down along its moving edge.

An object of this invention is to minimize the degradation which occurs to the edge of the moving plate when two plates are being joined using an explosive.

Another object of this invention is to provide an acceptor plate to minimize the breaking down of the end of the moving plate edge during explosive joining.

A further object of this invention is to have a separate accepter plate so positioned that when a moving plate is moved into joint forming position, the moving edge of the plate moves into intimate contact with an edge of said accepter plate to minimize the breaking down of the moving edge.

Other objects and advantages will be apparent from the specification and from the accompanying drawings which illustrate the invention.

FIGURE 1 is a top view showing two plates positioned on a holding die in readiness for ignition of the explosive charge with an accepter plate in position; and

FIGURE 2 is a side view of FIGURE 1.

With reference to FIGURES 1 and 2, two plates or sheets 2 and 4 are shown fixedly positioned in a holding die 6. The holding die 6'has a shim 8 positioned adjacent the end of the plate 4 on the die 6. Shim 8 is of the same thickness as the plate 4 so that the plate 2 can lie flat thereon and also extend in a fiat plate engaging fashion onto the end of plate 4.

The shim 8 and plate 2 are fixedly positioned by a plate or sheet engaging device 18 for fixedly holding the sheet 2 and shim 8 to the die 6 during the firing of the explosive charge. Each plate engaging device 18 comprises a bar 22 which is pivoted to a bracket 24 extending upwardly from the die 6. Each bracket 24 comprises two upstanding lugs. The free end of each bar 22 has an attach-detach mechanism which engages a bracket 26 on the die. A handle 28 is operable to engage or disengage the attach-detach device. While one specific holding device 18 has been shown, it is to be understood that other desirable devices can be used.

The holding die 6 includes an accepter plate 10 which is positioned over the plate 4 to fixedly hold it in position. Each end of the accepter plate 10 has an opening therein which permits a bolt 12 to pass therethrough. A washer or spacer 11 is positioned around each bolt 12 between said accepter plate 10 and die 6. Each bolt 12 threadedly engages the die 6. The angular end portion 34 of the plate 2 forms an angle a with the plate 4. When the plate 2 has been fixed in place, the accepter plate 10 fixedly engages plate 4 in place so that the free end of the moving angular portion 34 of plate 2 will come into intimate contact with the cooperating edge of the accepter plate 10 when it is moved into joining position by the firing of the explosive 40.

An explosive 40 is placed over the face of the angular portion of plate 2 located away from plate 4. This explosive extends over an area including the bend in the plate 2 to a location on said angular portion adjacent the moving end thereof. This explosive can be of the flexible sheet type. One type is the Du Pont EL-506 series. Further information on this type of explosive is set forth in US. Patent No. 2,992,087. A detonator 48 is positioned at the end of the explosive sheet 40.

The detonator 48 is held in position by a support 50. This support can be a block of clay which can be manually kneaded or manipulated to properly fit any location at which a detonator needs support. The detonator 48 can be of the standard commercial type which can be ignited by the closing of a circuit at a control point located a safe distance from the detonator and resulting explosion. While it is not part of this invention, one method of determining a satisfactory angle or and a satisfactory amount of explosive to be used is referred to in US. application Serial No. 248,002, an application to Carter et al., entitled Method of Explosively Forming a Scarf Type Joint which is being filed herewith.

The following references are set forth to provide a background of explosives and their use:

(1) Behavior of Metal Under Impulsive Loads, by John S. Rinehart and John Pearson, The American Society for Metals, 1954.

(2) Underwater Explosions, by Robert H. Cole, Princeton University Press, 1948.

(3) The Science of High Explosives, by Melvin A. Cook, Reinhold Publishing Corporation, 1958.

Without the use of the accepter plate It) the front or leading edge of the plate 2 upon which the explosive is affixed in effecting an explosive joint can be broken off or severely cracked as the joint is made. This degradation or deterioration is the greatest when the dissimilarity in the velocities of acoustic waves between the metal of the upper plate 2 to be joined and the surrounding media, which is generally air, inert gas, or vacuum as desired, is the greatest. The velocity of the acoustic wave in the metal plate is greater than that in the surrounding medium. This dissimilarity results in the reflection at the interface, or free surface, of that portion of the acoustic wave which is not transmitted to the surrounding medium. This reflection, or tension, wave then meets with the oncoming acoustic, or compressive, waves and causes a pressure spike due to the algebraic addition of these pressure waves. When the magnitude of this pressure spike exceeds the tensile strength of the metal, internal cracking or scabbing occur at the points where the tensile strength is exceeded. This results in a cracking of the upper plate leading edge and sometimes a complete deterioration of the upper plate over the entire area contacted by the explosive. See pages 341-342, The Science of High Explosives, by Dr. M. A. Cook, referenced above, for a more thorough description of this problem.

As referred to above, an acceptor plate 10 is attached to the surface of the lower plate 4 in such .a position that the leading edge of the upper plate 2 tightly contacts the facing edge of the accepter plate as it moves into joining contact with the lower plate. The intimate contact of the upper plate 2 land the accepter plate 10 allows the acoustic Waves to flow across the interface between the plates and thereby decrease the amount of energy mefiected at the leading edge of the upper plate. 'The accepter plate I10 as shown in FIGS. 1 land '2 is of such a size so as to receive the leading free end of the upper plate 2. In order to further minimize the amount of energy reflected, the accepter plate should be made of a material which has an equal or higher velocity of sound than the plate 2. The velocity of sound (C) :fior any material may be approximated with \a high degree of accuracy from fihe modulus of elasticity and the density of fih'e material by the followin g relation:

E=modulus of elasticity (p.s.i.) 'y density -(1b./in. C =velocity of sound (fps) 2.681 is a scaling factor which converts the final answer to fleet per second.

An example is set forth below showing materials on which subject invention has been used:

(1) Material of joined plates: 7075-T6 aluminum to 7075T6 .aluminum Thickness of joined plates: .125" Material of acoep'ter plate: 7075-T6 aluminum Thickness of acoepter plate: .125" Angle a used: 3 Sheet thickness of EL-S 06A: ,160"

It is to be understood that the invention is not limited to the specific iorm herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

We claim:

1. Method of making a joint from metals capable of being explosively joined comprising,

(a) selecting a first metal sheet end,

(b) selecting a second metal sheet part,

(c) forming an angular flange ion the sheet end,

(d) placing the sheet end in coopenating relationship to the sheet part with the angular flange extending over the sheet part so that it can be explosively driven against the sheet part and with said angular flange forming an acute angle with said sheet part,

(e) supporting the first metal sheet end and second metal sheet part,

(f) fixing an accepter sheet against said sheet part so that the free end of said flange will engage the end of said accepter plate when it is explosively driven against the sheet part,

(g) placing an explosive charge on said flange to drive it against said sheet part,

(11) igniting the explosive charge.

2. Method of making a joint from metals capable of being explosively joined comprising,

(a) selecting a first metal sheet end,

(b) selecting a second metal sheet part,

(c) forming an angular flange on the sheet end,

(d) placing the sheet end in coopenat-ing relationship to the sheet part with the angular flange extending over the sheet part so that it can be explosively driven against the sheet part and with said angular flange forming an acute angle with said sheet part,

(e) supporting the first metal sheet end and second metal sheet part,

(t) fixing an acceptor sheet of approximately the same thickness of said flanged sheet against said sheet part so that the free end of said flange will engage the end of said acceptor plate when it is explosively driven against the sheet part,

(g) placing an explosive charge on said flange to drive it against said sheet part,

(h) igniting the explosive charge.

3. Method of making a joint from metals capable of being explosively joined comprising,

(a) selecting a first metal sheet,

(b) selecting a second metal sheet,

(c) placing the end of the first sheet in cooperating relationship with the second sheet with the end of the first sheet extending over the second sheet so that the first sheet can be explosively driven against the second sheet,

( d) supporting the first and second metal sheets,

(e) fixing an acceptor sheet of approximately the same thickness as the first sheet with its end against said second sheet so that the free end of said first sheet will engage the end of said accepter sheet when it is explosively driven against the second sheet,

(f) placing an explosive charge on said first sheet adjacent the accepter sheet to join it with said second sheet,

(g) igniting the explosive charge.

5 4. Method of making a joint from materials capable of being explosively joined comprising,

(a) forming an angular flange along one plate end,

(b) placing the one plate and having the angular flange in cooperating relationship to a second plate portion with the flange projecting over the second plate portion forming an acute angle therewith,

(c) supporting the one plate end and second plate portion,

(d) fixing an accepter plate against said second plate portion so that the free end of said flange will engage the end of said accepter plate when it is explosively driven against the second plate portion,

(e) placing an explosive charge on said flange to drive it against said second plate portion,

(f) igniting the explosive charge.

5. Method of making a joint from metals capable of being explosively joined comprising,

(a) selecting a first metal sheet end,

(b) selecting a second metal sheet part,

(c) forming an angular flange on the sheet end,

(d) placing the sheet end in cooperating relationship to the sheet part with the angular flange extending over the sheet part so that it can be explosively driven against the sheet part and with said angular flange forming an acute angle with said sheet part,

(c) supporting the sheet end and sheet part,

(f) fixing an accepter sheet against said sheet part so that the free end of said flange will engage the end of said accepter sheet when in explosively joining position,

(g) placing an explosive charge on said flange to drive it against said sheet part,

(h) igniting the explosive charge.

6. Method of making a joint from metals capable of being explosively joined comprising,

(a) selecting a first metal sheet end,

(b) selecting a second metal sheet part,

(c) formingan angular flange on the sheet end,

(d) placing the sheet end in cooperating relationship to the sheet part with the angular flange extending over the sheet part so that it can be explosively driven against the sheet part and with said angular flange forming an acute angle with said sheet part,

(e) supporting the sheet end and sheet part,

(f) fixing an accepter sheet, having a velocity of sound therein equal to or higher than that of the sheet end having the angular flange, against said sheet part so that the free end of said flange will engage the end of said accepter plate when it is explosively driven against the sheet part,

(g) placing an explosive charge on said flange to drive it against said sheet part,

(h) igniting the explosive charge.

7. Method of making a joint from materials capable of being explosively joined comprising,

(a) forming an angular flange along one plate end,

(b) placing the one plate and having the angular flange in cooperating relationship to a second plate portion with the flange projecting over the second (55 plate portion forming an acute angle therewith,

(c) supporting the one plate end and second plate portion, (d) fixing an acccpter plate, having a velocity of sound therein at least as great as that of the one plate end having the angular flange, against said second plate portion so that the free end of said flange will engage the end of said acceptor plate when it is explosively driven against the second plate portion,

(e) placing an explosive charge on said flange to. drive 7 5 it against said second plate portion,

(f) igniting the explosive charge.

8. Method of making a joint from metals capable of being explosively joined comprising,

(a) forming an angular flange along one metal plate end,

(b) placing the one plate and having the angular flange in cooperating relationship to a second plate portion with the flange projecting over the second plate portion forming an acute angle therewith,

(c) supporting the second plate portion,

((1) fixing an accepter plate against said second plate portion so that the free end of said flange will engage the end of said accepter plate when it is explosively driven against the second plate portion, wherein said accepter plate has a velocity of sound C at least as great as that of the plate end having the angular flange where where :modulus of elasticity (p.s.i.)

'y=density (lb./in.

2.681=a scaling factor which converts the final answer to feet per second (e) placing an explosive charge on said flange to drive it against said second plate portion,

(f) igniting the explosive charge.

9. Method of making a joint from metals capable of being explosively joined comprising,

(a) selecting a first metal sheet,

(b) selecting a second metal sheet,

(c) forming an angular flange on the end of said first metal sheet,

(d) placing the end of the first metal sheet having the angular flange in cooperating relationship to the second metal sheet with the flange projecting over the second metal sheet forming an acute angle therewith,

(e) supporting the first and second metal sheets,

(i) fixing an accepter sheet against said second metal sheet so that the free end of said end of the first metal sheet will engage the end of said accepter plate when it is explosively driven against the second metal sheet,

(g) placing an explosive charge on said flange to drive it against said second metal sheet,

(11) igniting the explosive charge.

1% Method of making a joint from metals capable of being explosively joined comprising,

(a) selecting a first metal sheet,

(b) selecting a second metal sheet,

(c) placing the end of the first metal sheet in cooperating relationship to the second metal sheet with a space therebetween so that the end of the first metal sheet can be explosively driven against the second metal sheet,

(d) supporting the first and second metal sheets,

(e) fixing an accepter sheet against said second metal sheet so that the free end of said first will engage the end of said accepter plate when it is explosively driven against the second metal sheet,

(f) placing an explosive charge on said end of the first metal sheet to drive it against said second metal sheet,

(g) igniting the explosive charge.

References Cited by the Examiner UNITED STATES PATENTS 6/64 Cowan 29486 WHITMORE A. WILTZ, Primary Examiner. JOHN F. CAMPBELL, Examiner. 

1. METHOD OF MAKING A JOINT FROM METALS CAPABLE OF BEING EXPLOSIVELY JOINED COMPRISING, (A) SELECTING A FIRST METAL SHEET END, (B) SELECTING A SECOND METAL SHEET PART, (C) FORMING AN ANGULAR FLANGE ON THE SHEET END, (D) PLACING THE SHEET END IN COOPERATING RELATIONSHIP TO THE SHEET PART WITH THE ANGULAR FLANGE EXTENDING OVER THE SHEET PART SO THAT IT CAN BE EXPLOSIVELY DRIVEN AGAINST THE SHEET PART AND WITH SAID ANGULAR FLANGE FORMING AN ACUTE ANGLE WITH SAID SHEET PART, (E) SUPPORTING THE FIRST METAL SHEET END AND SECOND METAL SHEET PART, (F) FIXING AN ACCPETER SHEET AGAINST SAID SHEET PART SO THAT THE FREE END OF SAID FLANGE WILL ENGAGE THE END OF SAID ACCEPTER PLATE WHEN IT IS EXPLOSIVELY DRIVEN AGAINST THE SHEET PART, (G) PLACING AN EXPLOSIVE CHARGE ON SAID FLANGE TO DRIVE IT AGAINST SAID SHEET PART, (H) IGNITING THE EXPLOSIVE CHARGE. 